This article was published in the February 2012 issue of LEDs Magazine.
View the Table of Contents and download the PDF file of the complete February 2012 issue.
Adaptive lighting control is a necessity going forward given the energy crisis we face globally and the fact that lighting consumes a very large share of the energy used. Efficient solid-state lighting (SSL), using LED sources, is a step in the right direction for slashing energy usage, and controls that eliminate over-lighting can greatly enhance savings. Lighting manufacturers and companies dedicated to sensor and control products support adaptive-control scenarios today, although the networking schemes that link products are largely proprietary. Standards-based networks would enable interoperable products from multiple vendors, but a robust, standardized, lighting-centric network is still a work in progress.
The transition to LED lighting has sparked an increased interest in controls. LEDs are easily dimmable. Moreover dimming SSL delivers energy savings that track the lower light output in a near linear fashion. The efficiency of many LED drivers does drop slightly at less than full load, but the savings remain substantial. The savings that come with dimming aren’t as significant with many legacy sources.
The biggest obstacle to broader deployment remains the lack of a full network stack for lighting (see www.ledsmagazine.com/features/7/11/13 for a primer on network technology and the layers that comprise a network stack.) There are wired and wireless networks that could serve in lighting, but in every instance one or more required layers are missing. We will cover those shortcomings through the course of this article.
Let’s examine the current landscape of control schemes by first covering the approach lighting manufacturers are taking to attack the problem. We will then consider the technology that control specialists are offering that can enable systems that mix products from different vendors. Lastly we will look at the prospects for standardized networks.
The major lighting vendors all have some approach to control systems using either wired or wireless interconnects to link lighting and occupancy sensors, switches and dimmers, and light fixtures to a centralized controller. We won’t cover the breadth of technologies here, but will consider the approach of Acuity Brands.
Several of Acuity’s lighting-centric brands address controls. For example, the Roam brand targets networking of street lights. For indoor-lighting applications, the Sensor Switch brand includes a broad array of control products within the nLight family.
NLight relies primarily on a wired network infrastructure using the same Cat-5 cables used for office and home Ethernet networks. Indeed an nLight installation looks like an office network from a topology perspective. A software tool called SensorView resides on a PC and handles commissioning and control. The PC links to the nLight network using an Ethernet connection to one or more nGWY gateways.
Each gateway in turn connects to bridges. For example the nBRG 8 product includes 8 output ports that link to nLight network elements including sensors, wall panels, switches, power-switching modules, and nLight-enabled LED luminaires. Each gateway output can control a multi-element lighting zone with elements daisy-chained via Cat-5 cables.
Network enabled luminaires
Acuity offers the RTLED, ACLED, TLED, and VTLED luminaires through its Lithonia Lighting brand that come with the network connection and a driver equipped for nLight control. You can also add lighting elements to an nLight network that aren’t designed for such use. For example the nSP5 D relay and dimming module can both switch AC power to a third-party luminaire and provide 0-10V dimming control.
Sensor Switch has also demonstrated wireless connectivity options. For example, the wireless nPP WIFI module duplicates the functionality of the wired nPP16 relay pack that is a widely used element in nLight networks. The relay packs both switch power to 16A loads and act as a power source for downstream network elements that require a DC power supply.
The nPP WIFI communicates back to the gateway over a standard Wi-Fi network. Sensor Stream value stream manager Michael Clemens said, “It relies on an off-the-shelf 802.11b/g/n router” that ultimately links to the gateway device via Ethernet. Acuity has also mentioned wireless ZigBee links between gateways and bridges in various literature, although no such products are listed on the Sensor Switch website at this time.
Peruse the websites of other major lighting vendors and you will find similar proprietary networking schemes. Companies that specialize in control technologies, however, have a broader range of network elements, wireless support, and system controllers. And Lutron has perhaps the broadest array of offerings in the segment with products that target light-control in individual residential rooms, whole-house systems, and commercial-building systems. Moreover the lighting controls are part of a larger automation offering that includes control of HVAC systems, motorized window shades, and appliances.
Whole-house systems build on that functionality via wireless repeaters that extend the range of the network. And Lutron offers dedicated controllers such as the RadioRA 2 and HomeWorks systems that can control multiple rooms or zones. For commercial applications, or perhaps high-end residential, Lutron offers systems capable of controlling more zones and adds a wired interconnect capability called EcoSystem that is an enhanced version of the DALI standard for light control.
Lutron offers only a few luminaires under its Lutron and Ivalo brands. Instead it supports third-party lighting products with the combination of the lamp plug-in modules, wall dimmers, and a broad ballast and driver family that includes the Hi-lume A-Series LED driver family. Lutron has a long list of luminaire partners that offer Hi-lume as a driver option.
The driver offering is broad. Lutron's design development leader Ethan Biery said, “The Hi-lume A-Series has about 3000 different configurations and model numbers.” The specifiable options include characteristics such as drive current along with dimming support. In terms of dimming, Lutron offers models compatible with phase control, EcoSystem digital controls, and three-wire controls that have been used with fluorescent ballasts.
Proprietary or standard wireless?
Back to Clear Connect, Lutron has focused its wireless effort on a proprietary system in the 400-MHz frequency band that it believes offers optimal immunity from other signals from cordless phones, Wi-Fi, garage-door openers, and other potential sources of interference. Moreover Clear Connect uses what Lutron describes as a fixed network, meaning that after commissioning there is a predetermined path through the network between any sender and receiver. In contrast, mesh networks such as ZigBee formulate paths dynamically and rely on each network node to retransmit each received packet.
Lutron says that Clear Connect is more reliable and delivers commands more quickly than mesh networks. In reality ZigBee has been widely used in demanding factory-automation applications where latent command delivery can’t be tolerated. Moreover the mesh scheme eliminates the need for repeaters or for each sender and receiver to be within wireless range of one another.
But the biggest point of contention over a wireless scheme such as Clear Connect is the proprietary nature. Lutron could decide to license the technology to others. But a network based on an industry standard such as ZigBee should allow any manufacturer to build compatible products.
The operative word in the prior sentence is should. In actuality the ZigBee standard doesn’t include the full set of network layers required for interoperable lighting products. ZigBee does ensure reliable delivery of data packets. But it doesn’t include the upper network layers that would define lighting-specific protocols and commands. Such layers could still be added on top of ZigBee but today companies using ZigBee for lighting are adding their own proprietary lighting protocols.
Consider Adura Technologies. The company follows a strategy similar to Lutron but uses a ZigBee-based wireless network (Fig.1). The company offers ZigBee-enabled network elements that work with existing third-party sensors and luminaires. For example, an installation would require an Adura Wireless Sensor Interface to be mated with each occupancy or light sensor in an installation. Likewise each luminaire would require an Adura Wireless Light Controller. And the company offers Wireless Wall Control Interfaces that can switch an AC signal and implement phase-control dimming.
Adura also offers a ZigBee gateway that links the lighting network to the office network where a PC can handle commissioning and control. The Adura Lighting Control Software is a web-based platform that supports features such as scheduling. In fact the software can even be used remotely over the Internet. Ultimately the company hopes to have third-parties build luminaires and other network elements with integrated support for its wireless network.
Building an ecosystem
Daintree Networks has also developed a ZigBee-based, lighting-centric network scheme that it calls ControlScope. Unlike Adura, Daintree is not manufacturing any network elements other than a Wireless Area Controller that implements the gateway functionality and enables control and commissioning via the company’s ControlScope Manager software. For network elements, Daintree is attempting to build an ecosystem of third-party partners to support ControlScope.
At present Daintree lists more than a dozen companies as ControlScope Connected partners. The list includes LED-based planar-lighting specialist Lunera Lighting. Partner Finelite is an established player in the commercial-lighting space with luminaires based both on SSL and legacy sources. There are driver manufacturers on the list including eldoLED and manufacturers of sensors and actuators such as SimpleHomeNet. Still it’s tough to judge the traction that Daintree has in the market, because the company has yet to announce a major installation.
Lighting companies that want to develop a controls-centric product portfolio don’t necessarily require the help of a networking specialist such as Daintree or Adura. Semiconductor manufacturers are developing reference designs and software stacks that can speed the development of products such as network-enabled luminaires. For example at the recent Consumer Electronics Show (CES) in Las Vegas, Marvell announced a ZigBee-based smart lighting platform that utilizes its ICs. Marvell will supply reference software to its customers for free hoping to accelerate the controls marketplace.
Looking forward, the standards forecast is unclear. Ideally the industry will develop a standard that would allow interoperable products just as consumers can buy interoperable computer-network elements. The ZigBee Alliance has developed the ZigBee Building Automation layer that addresses controls for HVAC and other systems. And the organization is working on a lighting-centric upper-layer protocol called ZigBee Light Link.
ZigBee doesn’t inherently support the Internet Protocol (IP) that is the basis for the Internet and Ethernet networks. Of course a gateway can link ZigBee-enabled devices to the Internet. But an alternative protocol called 6LoWPAN (IPv6 over Low power Wireless Personal Area Network) is IP based and is gaining momentum.
At a recent IPSO (Internet Protocol for Smart Objects) Alliance event called the Internet of Things, NXP Semiconductors demonstrated a 6LoWPAN-based lighting network. The company has developed a 6LoWPAN protocol stack called JenNet-IP that works with some of its microcontrollers. The demonstration featured Android devices and iPads controlling smart lights via the Internet.
The 6LoWPAN protocol can operate over the same lower network layers defined in the IEEE 802.15.4 standard that also underlies ZigBee. But even the 802.15.4 physical and media-access-control layers aren’t a sure bet for a future universally-accepted lighting network.
Google, for instance, wants to insert itself deeper into our lives and Android provides a potential avenue. Last May at the Android Developers Conference, Google announced an initiative called Android @ Home and demonstrated a prototype of a smart LED-based retrofit lamp developed by Lighting Science Group.
Back in May we speculated that Android @ Home would be based on 802.15.4. Google has been pretty quiet on the subject. But recent rumors point to the company developing a simpler alternative to 802.15.4 that would be cheaper to implement enabling lower-cost smart objects such as controllable LED lamps. Google is expected to use 6LoWPAN in Android @ Home.
While Google isn’t targeting commercial lighting, it could impact that segment were it to deliver an open network that could be used by other companies. Meanwhile the quest for a lighting-centric network continues while proprietary deployments also escalate. Indeed there is little reason not to implement smart lighting today, especially in the commercial space. Such projects are paid back rapidly via reduced energy costs. And today’s proprietary networks will be compatible via gateways with future standardized technologies.